Conventionally, while a fabric is knitted, a yarn feeding port as a knitting member has been used in order to feed a knitting yarn at an appropriate timing to a knitting needle that performs a knitting operation. In order to knit fabric products, it is necessary to use, in a switching manner, a plurality of knitting yarns of various colors and functions. In weft knitting machines of a V-shaped bed-type in which at least a pair of needle beds of the front and the rear is provided and in which the front and rear needle beds are opposed to each other with a needle bed gap interposed therebetween, a general configuration is such that a plurality of yarn guide rails are installed above the needle bed gap, yarn feeders provided with yarn feeding ports are led to travel along the yarn guide rails, and knitting yarns are switched by switching the yarn feeders. The yarn feeders are selected by a bringing and switching apparatus provided at a bridge that couples between carriages provided respectively on the front and rear needle beds such that the yarn feeders are used while being brought by the carriages (see Japanese Examined Patent Publication JP-B2 63-23301 (1988) and Japanese Examined Patent Publication JP-B2 06-65781 (1994), for example).
A method is also known by which knitting yarns are switched by directly mounting and dismounting yarn guide tubes serving as the yarn feeding ports on/from carriages instead of using yarn feeders or other components traveling on yarn guide rails. Examples thereof include a color changing apparatus for a plain knitting machine in which a magazine that carries a plurality of yarn guide tubes referred to as yarn guide small nuts is disposed at one end of a needle bed, and when the carriage is positioned at the magazine, a yarn guide small nut mounted on the carriage is handed over to an empty carrying member, and one of carrying members that carry the yarn guide small nuts is mechanically switched from a still mode to a handing-over mode, so that the yarn guide small nut is received by the carriage (see Japanese Unexamined Patent Publication JP-A 47-20452 (1972), for example). Furthermore, the applicant of the invention also has proposed a weft knitting machine provided with a yarn guide tube changing apparatus for transferring yarn guide tubes by using a magnetic force (see Japanese Unexamined Patent Publication JP-A 09-268455 (1997), for example).
Products whose fabric is to be knitted with a weft knitting machine include products, such as gloves and socks, with a comparatively small stitch width. In order to efficiently produce these products with a small stitch width, it is required that carriages travel with a small width, at a high speed, and at a high frequency of traveling back and forth. Especially in a case where gloves are knitted, it is necessary that tubular plain stitch for each of five fingers and tubular plain stitch for an entire palm are repeated with a small width. In the methods for bringing the yarn feeding ports using the yarn guide rails as in JP-B2 63-23301 and JP-B2 06-65781, the bringing and switching apparatus such as a bringing pin is provided on the side of the carriages, and thus the carriages become bulky and heavy, so that the durability is impaired in a weft knitting machine in which travels are heavily repeated with a small width and at a high speed. Furthermore, when the frequency at which the carriages travel back and forth becomes high, there is a possibility that the yarn guide rails vibrate or are warped, and thus the yarn feeding becomes unstable. In addition, the yarn guide rails occupy the space above the narrow needle bed gap, and thus an operation of letting yarns pass through yarn feeders mounted on the yarn guide rails and a maintenance operation become difficult.
In the color changing apparatus as shown in JP-A 47-20452, the yarn guide small nuts are unstable because they are gripped between flexible members, and thus the yarn guide small nuts may be likely to vibrate when modes are switched from a still mode to a handing-over mode. Furthermore, a space in which the yarn guide small nuts are gripped is necessary, and thus an operation of letting yarns pass through the yarn guide small nuts, for example, may be complicated. In the yarn guide tube changing apparatus as in JP-A 09-268455, the length in which magnets are provided on the front and rear faces of the yarn guide tubes is necessary, and thus an operation of letting yarns pass through the yarn guide tubes is complicated. Since the yarn guide tubes are kept with a magnetic force, there is a possibility that the position of the yarn guide tubes is shifted due to vibrations or impacts.